Do beavers promote the invasion of non-native Tamarix in the Grand Canyon riparian zone?

Site-Occupancy Monitoring of an Ecosystem Indicator: Linking Characteristics of Riparian Vegetation to Beaver Occurrence

“…In general, the vegetation composition follows a moisture gradient, with marsh species and obligate riparian species situated adjacent to the shoreline and facultative riparian and xerophytic species located farther upslope . Further details regarding geomorphology and riparian vegetation can be found in Schmidt and Graf (1990), Stevens et al (1995), Ralston et al (2008), and Mortenson et al (2008).…”

“…For instance, the area of riparian vegetation has increased by more than 50% and continues to expand , and marsh communities have expanded throughout the corridor (Stevens et al 1995). Mortenson et al (2008) found that after accounting for river geomorphology, beaver presence in the Grand Canyon was more likely in areas with higher coverage of a particular type of plant (i.e., Tamarix).…”

Distribution and Abundance of Saltcedar and Russian Olive in the Western United States

“…Examples of rivers that support dense, nearly monotypic stands of saltcedar include the Lower Colorado from Lake Mead (on the Nevada/Arizona border) to the U.S.-Mexico border (Nagler et al, 2007), the Rio Grande below Elephant Butte Reservoir in southern New Mexico (Hudgeons et al, 2007), and the Pecos River in New Mexico and Texas (Hart et al, 2005) ( Figure 4). Floodplains vegetated with mixtures of saltcedar and native trees represent the most common current condition along western river segments, including the following: Middle Rio Grande (Dahm et al, 2002;Akasheh et al, 2008;Walker et al, 2008); the Lower San Pedro (Brand et al, 2008); the San Juan River below Navajo Dam in Colorado, New Mexico, and Utah (authors' observations); the Colorado River below Glen Canyon Dam in Grand Canyon (Groeneveld and Watson, 2008;Mortenson et al, 2008); the Bill Williams River below Alamo Dam in Arizona (Shafroth et al, 2002); the Salt River above Roosevelt Lake and the Agua Fria River in Arizona (Stromberg et al, 2007b;Boudell and Stromberg, 2008); the Arkansas River in Colorado (Nelson and Wydoski, 2008); and the delta of the Colorado River in Mexico .…”

The influence of floods and precipitation on Tamarix establishment in Grand Canyon, Arizona: consequences for flow regime restoration

“…Salix gooddingii C.R. Ball was formerly more common, but the few remaining stands are threatened by beaver foraging, lack of springtime recruitment floods, and post-dam coarsened sand substrata (Mast and Waring 1997;Mortenson et al 2008;Stevens 1989).…”